Apparatus and method for active vibration control of hybrid electric vehicle

ABSTRACT

The present disclosure relates to active vibration control of a hybrid electric vehicle. One form provides a method that may include setting up a period of fast Fourier transform (FFT) and performing FFT of an engine speed or a motor speed corresponding to the period of the FFT from a reference angle signal; setting up a reference spectrum; extracting vibration components to be removed based on information of the reference spectrum; selecting and adding a removal object frequency from the vibration of each frequency and performing inverse FFT; determining a basic amplitude ratio according to the engine speed and the engine load; determining an adjustable rate which decreases an anti-phase torque as a change amount of the engine speed is decreased; and performing active vibration control of each frequency based on the information of the basic amplitude ratio, the adjustable rate, and the engine torque.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0177460, filed in the Korean Intellectual Property Office on Dec. 11, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Field of the Disclosure

The present disclosure relates to an apparatus and a method for active vibration control of a hybrid electric vehicle. More particularly, the present disclosure relates to an apparatus and a method for active vibration control of a hybrid electric vehicle that controls unsteady vibration by analyzing a frequency spectrum through fast Fourier transform (FFT).

(b) Description of the Related Art

A hybrid vehicle is a vehicle using two or more different kinds of power sources, and is generally a vehicle that is driven by an engine that obtains a driving torque by burning fuel and a motor that obtains a driving torque with battery power.

Hybrid electric vehicles can be provided with optimum output torque, depending on how the engine and the motor are operated while the vehicles are driven by the two power sources, that is, the engine and the motor.

Hybrid electric vehicles may form various structures using the engine and the motor as power sources, and hybrid electric vehicles are classified as a TMED (Transmission Mounted Electric Drive) type, in which the engine and the motor are connected by an engine clutch and the motor is connected to the transmission, and an FMED (Flywheel Mounted Electric Drive) type, in which the motor is directly connected to a crankshaft of the engine and connected to the transmission through a flywheel.

From among these, since the FMED type of the hybrid electric vehicle is very noisy and has severe vibration, vibration reduction thereof is being studied. A method of frequency analysis which extracts the vibration component is normally used for this.

An analog method using a band pass filter has been used in a conventional frequency analysis, wherein the analog method of analysis determines whether or not a frequency is abnormal based on an amplitude of each expected point of a frequency band.

However, distinguishing between the vibration component of the engine and the vibration of the noise component is difficult, and unnecessary over-control of the vibration negatively affects aspects of control efficiency and energy management. Further, because it is only possible to create and synchronize a reference signal with respect to a specific frequency in the conventional frequency analysis, comprehensive and active control of other frequencies which may be additionally generated is not performed.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY

The present disclosure has been made in an effort to provide an apparatus and a method for active vibration control of a hybrid electric vehicle, having advantages of elaborately controlling an abnormal vibration component through an entire frequency spectrum analysis using FFT (fast Fourier transform) and reflecting a change of a surrounding frequency component in real time by feedback.

An exemplary form of the present disclosure provides a method for active vibration control of a hybrid electric vehicle that may include detecting an engine speed or a motor speed; selecting a reference angle signal based on position information of a motor or an engine; setting up a period of fast Fourier transform (FFT) and performing FFT of the engine speed or the motor speed corresponding to the period of the FFT from the reference angle signal; setting up a reference spectrum according to an engine speed and an engine load; extracting a vibration components to be removed based on information of the reference spectrum; selecting and adding a removal object frequency from the vibration of each frequency and performing inverse FFT; determining a basic amplitude ratio according to the engine speed and the engine load; determining an adjustable rate which decreases an anti-phase torque as a change amount of the engine speed is decreased; and performing active vibration control of each frequency based on the information of the basic amplitude ratio, the adjustable rate, and the engine torque.

The reference angle signal may be set by dividing by a number (m) of resolver poles based on information of the position of the motor or set up the reference angle between top dead center (TDC) and bottom dead center (BDC) of the number one cylinder or the number four cylinder based on information of the position of the engine.

The FFT period may be set in consideration of a cylinder and a stroke of the engine.

The analysis of the FFT signal may calculate a amplitude and phase information of each frequency.

The frequency component that the FFT signal is greater than the reference spectrum may be selected as the vibration component to be removed.

The vibration component to be removed is removed by outputting the motor torque corresponding to an inverse value of a value by multiplying a reference signal obtained by inverse FFT, the engine torque, the basic amplitude ratio and the adjustable rate.

Another exemplary form of the present disclosure provides a control apparatus for active vibration control of a hybrid electric vehicle including an engine and a motor as a power source that may include a position sensor configured to detect position information of the engine or the motor; and a controller configured to select a reference angle signal on the basis of a signal from the position sensor, perform fast Fourier transform (FFT) analysis, extract a vibration component to be removed through the FFT analysis, generate a reference signal by performing inverse FFT, and perform active vibration control of each frequency by reflecting a basic amplitude ratio, a predetermined adjustable rate which decreases an anti-phase torque as a change amount of the engine speed is decreased, and an engine torque to the reference signal.

The controller may set up a reference spectrum according to an engine speed and an engine load, and extract the vibration component to be removed by comparing the reference spectrum with the FFT signal.

The controller may generate the reference signal by performing inverse FFT after selecting and summing a removal object frequency from each frequency vibration through FFT analysis.

The controller may remove the vibration component to be removed by outputting the motor torque corresponding to an inverse value of a value by multiplying the reference signal generated created by the inverse FFT, the basic amplitude ratio, the adjustable rate, and the engine torque.

The controller may set up the reference angle signal by dividing by a number (m) of resolver poles based on information of the position of the motor or set up the reference angle between top dead center (TDC) and bottom dead center (BDC) of a number one cylinder or a number four cylinder based on information of the position of the engine.

The controller may set up an FFT period in consideration of a cylinder and stroke of the engine, and analyzes the FFT signal by a calculated amplitude and phase information of each frequency.

As described above, according to the exemplary form of the present disclosure, the vibration may be actively controlled, because the exact vibration component of each frequency may be extracted through FFT frequency spectrum analysis. Therefore, since the determination system of the reference angle of the engine and the motor may be utilized as it is, an additional device or an algorithm for signal synchronization as used in the conventional art may be eliminated.

In addition, the adjustment amount of vibration and frequency which is the object of the vibration control may be controlled individually, it is possible to prevent inefficiency which is from the control when the vibration is over-removed and the fuel consumption may be improved as the motor torque is increased when the engine is accelerated. Thus, precise and efficient active control may be performed through the feedback control in real time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an apparatus for active vibration control of a hybrid electric vehicle.

FIG. 2 is a flowchart illustrating a method for active vibration control of a hybrid electric vehicle.

FIG. 3 is a drawing illustrating vibration reduction to which a method for active vibration control of a hybrid electric vehicle is applied in case that a change amount of an engine speed is decreased.

FIG. 4A to 4F are graphs for explaining a method for active vibration control of a hybrid electric vehicle is applied.

DETAILED DESCRIPTION

In the following detailed description, only certain exemplary forms of the present disclosure have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described forms may be modified in various different ways, all without departing from the spirit or scope of the present disclosure.

Throughout this specification and the claims which follow, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

Like reference numerals designate like elements throughout the specification.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general including hybrid vehicles, plug-in hybrid electric vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid electric vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

Additionally, it is understood that some of the methods may be executed by at least one controller. The term “controller” refers to a hardware device that includes a memory and a processor configured to execute one or more steps that should be interpreted as its algorithmic structure. The memory is configured to store algorithmic steps and the processor is specifically configured to execute said algorithmic steps to perform one or more processes which are described further below.

Furthermore, the control logic of the present disclosure may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, a controller, or the like. Examples of computer readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media are stored and executed in a distributed fashion, e.g., by a telematics server or a controller area network (CAN).

An exemplary form of the present disclosure will hereinafter be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an apparatus for active vibration control of a hybrid electric vehicle.

As shown in FIG. 1, an apparatus for active vibration control of a hybrid electric vehicle includes an engine 10, a motor 20, a position sensor 25, a clutch 30, a transmission 40, a battery 50, and a controller 60.

The engine 10 outputs power by combusting fuel as a power source while turned on. The engine 10 may be various disclosed engines such as a gasoline engine or a diesel engine using conventional fossil fuel. The rotation power generated from the engine 10 is transmitted to the transmission 40 side through the clutch 30.

The motor 20 is operated by a 3-phase AC voltage applied from the battery 50 through an inverter to generate torque, and operates as a power generator and supplies regenerative energy to the battery 50 in a coast-down mode.

In the exemplary form of the present disclosure, the motor 20 may be directly connected to the crankshaft of the engine 10.

The position sensor 25 detects position information of the engine 10 or the motor 20. That is, the position sensor 25 may include a crankshaft position sensor that detects a phase of the crankshaft or a motor position sensor that detects a position of a stator and a rotor of the motor. The controller 60 may calculate an engine speed by differentiating the rotation angle detected by the crankshaft position sensor, and a motor speed may be calculated by differentiating the position of the stator and the rotor of the motor detected by the motor position sensor. The position sensor 25 may be additional speed sensor (not shown) for measuring the engine speed or the motor speed.

The clutch 30 is disposed between the motor 20 connected to the crankshaft of the engine 10 and the transmission 40, and switches power delivery to the transmission 40. The clutch 30 may be applied as a hydraulic pressure type of clutch or dry-type clutch.

The transmission 40 adjusts a shift ratio according to a vehicle speed and a running condition, distributes an output torque by the shift ratio, and transfers the output torque to the driving wheel, thereby enabling the vehicle to run. The transmission 40 may be applied as an automatic transmission (AMT) or a dual clutch transmission (DCT).

The battery 50 is formed with a plurality of unit cells, and a high voltage for providing a driving voltage to the motor 20 is stored at the battery 50. The battery 50 supplies the driving voltage to the motor 20 depending on the driving mode, and is charged by the voltage generated from the motor 20 in the regenerative braking.

The controller 60 selects a reference angle signal on the basis of a signal from the position sensor 25, performs fast Fourier transform (FFT), extracts a vibration component to be removed through the FFT analysis, generates a reference signal by performing inverse FFT, and performs active vibration control of each frequency by reflecting a basic amplitude ratio, a predetermined adjustable rate such that an anti-phase torque is decreased as a change amount of the engine speed is decreased, and an engine torque to the reference signal. The reference signal may mean an inverse FFT signal of the vibration components to be removed according to frequencies.

For these purposes, the controller 60 may be implemented as at least one processor that is operated by a predetermined program, and the predetermined program may be programmed in order to perform each step of a method for active vibration control of a hybrid electric vehicle according to an exemplary of the present invention.

Various embodiments described herein may be implemented within a recording medium that may be read by a computer or a similar device by using software, hardware, or a combination thereof, for example.

According to hardware implementation, the embodiments described herein may be implemented by using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, and electric units designed to perform any other functions.

In software implementations, forms such as procedures and functions described in the present forms may be implemented by separate software modules. Each of the software modules may perform one or more functions and operations described in the present disclosure. A software code may be implemented by a software application written in an appropriate program language.

Hereinafter, a method for active vibration control of the hybrid electric vehicle according to an exemplary form of the present disclosure will be described in detail with reference to FIG. 2 to FIG. 4.

FIG. 2 is a flowchart illustrating a method for active vibration control of a hybrid electric vehicle, and FIG. 3 is a drawing illustrating vibration reduction to which a method for active vibration control of a hybrid electric vehicle is applied in case that a change amount of an engine speed is decreased.

As shown in FIG. 2, an active vibration control method of the hybrid electric vehicle is started when the position sensor 25 detects position information of the engine 10 or the motor 20 at step S100, and the controller 60 may detect engine speed or motor speed using the position information of the engine 10 or the motor 20 at step S100 (refer to FIG. 4A). The controller 60 selects the reference angle signal based on the signal of the position sensor 25 at step S110. That is, the controller 60 selects the reference angle signal according to information of positions of the engine 10 and the motor 30 (refer to FIG. 4A).

The controller 60 may set up the reference angle signal by dividing by a number (m) of resolver poles based on information of the position of the motor 20, or may set up the reference angle signal between top dead center (TDC) and bottom dead center (BDC) of the number one cylinder or the number four cylinder based on information of the position of the engine 10. For example, the controller 60 may select the reference angle signal based on the information of the position of the motor 20, and may create the reference angle signal by dividing 16 poles signal into eight (8). The reference angle signal means a start point for performing FFT.

After that, the controller 60 sets up a period of the FFT for performing at step S120. The controller 60 may set up the entire period in consideration of a cylinder and stroke of the engine 10. For example, if the engine 10 has four cylinders and four strokes, the crank angle may be 720 degrees.

When the FFT period is set up in the step S120, the controller 60 analyzes the FFT signal at step S130. That is, the controller 60 performs the FFT of the engine speed, an engine acceleration, a rotational period of the engine, the motor speed, a motor acceleration, or a rotational period of the motor corresponding to the period of the FFT from the reference angle signal (refer to FIG. 4B). The controller 60 may calculate amplitude and phase information of each frequency by analyzing the FFT signal.

In addition, the controller 60 sets up a reference spectrum according to the engine speed and the engine load at step S140. That is, the controller 60 may set up a vibration reference value of each frequency according to an operating point of the engine.

When the reference spectrum is set up in the step S140, the controller 60 extracts a vibration component to be removed at step by comparing the FFT signal with the reference spectrum at step S150. That is, the controller 60 may select an object requiring vibration control in a compared result value of the FFT analysis and the predetermined vibration reference value. The controller 60 may extract the frequency component that the FFT signal is greater than the reference spectrum as the vibration component to be removed. For example, referring to FIG. 4B, f2 frequency component may be selected as a frequency component to be removed. Since the reference spectrum means normal vibration components according to the engine speed and load, the controller 60 determines the frequency component that the FFT signal is greater than the reference spectrum as abnormal vibration components to be removed.

As shown in FIG. 3, a amplitude and phase of vibration components of each frequency calculated by performing FFT analysis is illustrated in left upper side of the drawing.

When the vibration components to be removed is selected in the step S150, the controller 60 sums the vibration components to be removed according to frequencies, and performs inverse FFT to create a reference signal at step S160 (refer to FIG. 4C). As described above, the reference signal means inverse FFT signal of the vibration components to be removed.

When the reference signal is generated by performing the inverse FFT in the step S160, the controller 60 determines a basic amplitude ratio according to the engine speed and the engine load at step S170. Herein, the basic amplitude ratio according to the engine speed and load may be determined in advance by a predetermined map.

In addition, the controller 60 determines an adjustable rate which decreases an anti-phase torque as a change amount of the engine speed is decreased at step S180.

As shown in FIG. 3, the anti-phase torque which overlaps the component of vibration to be removed is illustrated as a dotted line in left lower side of the drawing. Herein, if the change amount of the engine speed is decreased, the adjustable rate may be set up such that the anti-phase torque is decreased in a negative direction as illustrated by a solid line.

After that, the controller 60 performs active vibration control based on information of the amplitude ratio, the adjustable rate, and the engine torque at step S180. That is, the controller 60 may remove all the positive components and negative components of the vibration components by outputting the motor torque corresponding to an inverse value of a value by multiplying the reference signal created by inverse FFT, the engine torque and the basic amplitude ratio (refer to FIG. 4D). Since the reference signal is expressed as speed according to time, the controller 60 removes the vibration components to be removed by reflecting the engine torque and the basic amplitude ratio to the reference signal and transforming the reference signal to torque component. That is, as shown in FIGS. 4E and 4F, it is possible to control the engine speed or the motor speed that the frequency components corresponding to the reference spectrum are remained.

Referring to FIG. 3, the adjustable rate is applied to the vibration component extracted through the FFT analysis, and since the decreased anti-phase torque as the change amount of the engine speed is decreased is added, it is controlled such that the object to be removed is removed and a required vibration component remains as described in right side of the drawing.

As shown in FIG. 4, if a vehicle is decelerating in which the change amount of the engine speed is decreasing, the predetermined adjustable rate may be applied so as to decrease the anti-phase torque. At this time, since vibration of the engine is decreased as the engine speed is decreased, effect of vibration reduction can be maintained even though the anti-phase torque is decreased in accordance with the adjustable rate. Therefore, vibration can be actively reduced with minimizing energy consumption. Further, remained energy may be used for battery charging.

As described above, the vibration may be actively controlled, because the exact vibration component of each frequency may be extracted through FFT frequency spectrum analysis. Therefore, since the determination system of the reference angle of the engine and the motor may be utilized as it is, an additional device or an algorithm for signal synchronization as used in the conventional art may be eliminated.

In addition, the adjustment amount of vibration and frequency which is the object of the vibration control may be controlled individually, it is possible to prevent inefficiency which is from the control when the vibration is over-removed and the fuel consumption may be improved as the motor torque is increased when the engine is accelerated. Thus, precise and efficient active control may be performed through the feedback control in real time.

While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed forms. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

What is claimed is:
 1. A method for active vibration control of a hybrid electric vehicle, comprising: detecting, by a controller of the hybrid electric vehicle, an engine speed of a motor included in the hybrid electric vehicle and a motor speed of a motor included in the hybrid electric vehicle; selecting, by the controller of the hybrid electric vehicle, a reference angle signal based on position information detected by a position sensor, the position information including motor position information detected from the motor or engine position information detected from the engine; setting, by the controller of the hybrid electric vehicle, a period for applying a fast Fourier transform (FFT) based on an engine characteristic of the engine corresponding to the reference angle signal; determining, by the controller of the hybrid electric vehicle, a FFT signal based on performing, using the period, the FFT on the engine speed or the motor speed, the FFT signal comprised of a plurality of frequency components; determining, by the controller of the hybrid electric vehicle, a reference spectrum covering the plurality of frequency components according to the engine speed and an engine load of the engine; comparing, by the controller of the hybrid electric vehicle, the FFT signal with the reference spectrum for each of the frequency components; extracting, by the controller of the hybrid electric vehicle, vibration components from the FFT signal based on the comparison of the FFT signal with the reference spectrum, wherein the extracted vibration components are portions of each frequency component of the FFT signal that are greater than the reference spectrum; selecting and adding, by the controller of the hybrid electric vehicle, a removal object frequency from a vibration of each frequency component and determining a summed removal object by adding each of the extracted vibration components; determining, by the controller of the hybrid electric vehicle, a reference signal based on performing an inverse FFT on the summed removal object; determining, by the controller of the hybrid electric vehicle, a basic amplitude ratio of the engine speed to the engine load; determining, by the controller of the hybrid electric vehicle, an adjustable rate which decreases an anti-phase torque as a change in the engine speed decreases; and performing, by the controller of the hybrid electric vehicle, active vibration control of each frequency component by controlling the engine speed or controlling the motor speed based on a value calculated from the basic amplitude ratio, the adjustable rate, the engine torque, and the reference signal.
 2. The method of claim 1, wherein the reference angle signal is set by dividing by a number of resolver poles based on information of the position of the motor or the reference angle is set up between top dead center (TDC) and bottom dead center (BDC) of the number one cylinder or the number four cylinder based on information of the position of the engine.
 3. The method of claim 1, wherein the period is set based on engine characteristics including a number of cylinders of the engine and a stroke of the engine.
 4. The method of claim 1, wherein the analysis of the FFT signal calculates an amplitude and phase of each frequency component.
 5. The method of claim 1, further comprising outputting, by the controller of the hybrid electric vehicle, the motor torque corresponding to an inverse value of a value by multiplying the reference signal, the engine torque, the basic amplitude ratio and the adjustable rate. 